Re: [Qemu-devel] [PATCH 2/2] target-i386: Fix default Hypervisor level for hypervisor-vendor=kvm.

[Eduardo Habkost]

On Tue, Sep 18, 2012 at 10:49:53AM -0400, Don Slutz wrote:
> From http://lkml.indiana.edu/hypermail/linux/kernel/1205.0/00100.html
> EAX should be KVM_CPUID_FEATURES (0x40000001) not 0.
> 
> If kvm is not configured, the additional option of hypervisor-level=1
> (or hypervisor-level=0x40000001) needs to be specified to get this.
> ---
>  target-i386/cpu.c |   12 +++++++++++-
>  1 files changed, 11 insertions(+), 1 deletions(-)
> 
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 6e43eff..d73b0a8 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -1248,7 +1248,12 @@ static char *x86_cpuid_get_hv_vendor(Object *obj, 
> Error **errp)
>                 env->cpuid_hv_level == CPUID_HV_LEVEL_XEN) {
>          pstrcpy(value, sizeof(value), "xen");
>      } else if (!strcmp(value, CPUID_HV_VENDOR_KVM) &&
> -               env->cpuid_hv_level == 0) {
> +#if defined(CONFIG_KVM)
> +               env->cpuid_hv_level == KVM_CPUID_FEATURES
> +#else
> +               env->cpuid_hv_level == 0
> +#endif
> +         ) {
>          pstrcpy(value, sizeof(value), "kvm");
>      }
>      return value;
> @@ -1281,6 +1286,11 @@ static void x86_cpuid_set_hv_vendor(Object *obj, const 
> char *value,
>          }
>          pstrcpy(adj_value, sizeof(adj_value), CPUID_HV_VENDOR_XEN);
>      } else if (!strcmp(value, "kvm")) {
> +#if defined(CONFIG_KVM)
> +        if (env->cpuid_hv_level == 0) {
> +            env->cpuid_hv_level = KVM_CPUID_FEATURES;
> +        }
> +#endif

If CPUID[0x40000000].EAX set to 0 is documented as equivalent to having
it set to 0x40000001 (KVM_CPUID_FEATURES), why the confusing checks for
CONFIG_KVM? Why not always set it to KVM_CPUID_FEATURES?

-- 
Eduardo